Forum Post: RE: AM6548: ATF: Unhandled Exception in EL3 when running from DDR4, and DDR4 Questions

Hi James, quick question about reading the MR registers using DDRCTL_MRCTRL0/1/2. I cannot seem to get it to work. The following is the code I use to do it: void ddr_dump_mr_regs (struct am654_ddrss_desc *ddrss) { volatile int regVal = 0; // Read from all DDR MR registers for (int i = 0; i 0) { regVal = ddrss_ctl_readl(DDRSS_DDRCTL_MRCTRL0); } printf("MR%d val: 0x%08x \n", i, ddrss_ctl_readl(DDRSS_DDRCTL_MRCTRL1)); } } We are only single rank here, with 2 devices. But MRCTRL1 seems to always return 0. Upon reading the TRM, it seems that MRCTRL1 is only for "Mode register write data for all non-LPDDR2/non-LPDDR3/non-LPDDR4 modes.". So is there anywhere we can actually read the MR registers? And are these MR registers different from the DDRPHY_MR0-7_DDR4 registers? Could we not just read from those? Thanks, Ben